Upheavals like the one in Ferguson, Mo., do not happen all of the sudden. They are not about a white police officer shooting a black teenager. They are about everything that happened before that moment. They are about every real and perceived slight and grievance accumulated over months and years.

The riot we call the Boston Massacre was the culmination of years of hard feelings between colonists and British soldiers. The colonists resisted import duties by boycotting British goods. This, naturally, encouraged smuggling, which the colonial secretary countered by sending a war ship and soldiers. The captain felt perfectly justified impressing Bostonians into service. Bostonians disagreed. The British soldiers, restless on shore and short of money, hired on for casual labor, which took jobs away from colonists; at the end of the day, often as not, they all wound up in the same taverns, drinking rum and trading insults.

In February 1770, an 11-year-old boy was killed when a customs official fired off a shotgun in an attempt to disperse a mob surrounding his house.

In March, a British sentry struck a boy for insulting an officer. A crowd gathered. Reinforcements were sent to rescue. Snowballs, insults and bits of debris were hurled at the soldiers, until one of them was knocked down by a rock. We all know where it went from there.

This is not to equate the goings on in Ferguson with the Boston Massacre. But the Boston Massacre didn’t just happen all at once, or because of one single event, and neither, I’d be willing to bet, did Ferguson.